The popularity of racket sports has continuously increased over the past 10-20 years. Concomitant with this increase in popularity are the technological advances in the sports equipment. In particular, the art of design and manufacture of racket frames has developed in an effort to improve racket performance. As an example, with respect to tennis rackets, the racket frames have evolved from the use of wood as the predominant material of choice, to the steel-shafted rackets of the early 1970s, to the graphite and ceramic composites of today.
One of the most recent trends in racket design is the use of the so-called "wide body" rackets as exemplified by U.S. Pat. No. 4,664,380. This racket type has a thickness, as measured orthogonal to the stringing plane, which is larger in the throat portion, relative to the prior art. Further, the racket frame thickness tapers continuously from the throat portion to the top of the head and also tapers continuously from the throat portion to the handle. Additional "wide body" rackets of the prior art are manufactured by Prince.RTM. Mfg. This family of rackets has a constant taper, whereby the racket frame thickness progressively becomes thicker from the handle to the top of the head. The constant taper system of the Prince.RTM. racket allows for greater stiffness in the top of the head portion.
Although the overall performance of these rackets may be improved relative to other prior art, a large segment of tennis players may find these rackets unsuitable. For example, one of the important parameters of a tennis racket is the stiffness of the racket. The stiffness of a racket is defined to be the amount of racket frame resistance to a force applied orthogonal to the stringing plane. Generally, the stiffer the racket the more vibration at impact is transmitted to the tennis player. Although this vibration can be a major cause of many arm injuries, most tennis players require some measure of stiffness, because stiffness in the racket gives the player more control and accuracy and less "trampolining" effect. However, the two examples of "wide body" rackets described above may be overly stiff for many players because of the substantial thickness of the rackets, thus increasing the possibility of injury.
Moreover, another major disadvantage of the prior art is that because of the thickness of the frames, increased air resistance may be encountered during use of the tennis racket. Although air resistance with these prior art rackets may be relatively low when the racket is swung in a direction orthogonal to the stringing plane, if the racket is swung in any other direction, air resistance increases dramatically. This is because the cross-sectional profile of the frames described above can best be described as an elongated oval. Thus, the frames have a small aerodynamic profile when viewed orthogonal to the stringing plane and a much larger aerodynamic profile when viewed parallel to the stringing plane. Further, it can be appreciated that in most tennis strokes the racket does not travel directly orthogonal to the string plane, but rather in a "low-to-high" aerodynamic profile motion, thus exposing the thickest racket profile to the air when the racket is traveling at its maximum speed. In some strokes, such as the serve, the direction of racket travel may be nearly parallel to the stringing plane, once again exposing the largest racket profile to the air.
In contrast, the present invention incorporates the advantages of "wide body" rackets without the problems of excessive racket stiffness or excessive aerodynamic drag of the prior art rackets. Specifically, a lightweight tennis racket having a frame of adequate stiffness and a circular cross section is disclosed.